1. Field of the Invention
This invention relates to a process for the beneficiation of maximum amounts of kish slag waste material for the purpose of deriving an iron based product sufficient in total ferrous content to be reusable in a variety of forms in a plurality of industrial processes in the iron and/or steel producing industry, while also producing a viable by-product with minimal ferrous content.
2. Description of the Prior Art
Desulf slag or kish slag which contains very low iron content is a waste material by-product of the steel and iron producing industry which, in the form accumulated, is generally considered to be impractical for purposes of reuse in conventional processes associated with the industry. One exception to this is the possible use of this low iron content material as an additive to sinter plants. In addition to the low iron content in the form that kish slag is produced, it also comprises particles or fines of extremely small size. Accordingly, the combination of low iron content and extremely small sizing of the particles or fines eliminates its use as a practical addition to processes in the steel or iron making industry.
As a result, steel mills accumulate extremely large quantities of this waste material resulting in problems related to the disposal of such waste material in a manner which is both economical and which complies with environmental restrictions of a given geographical area. For example, an area such as Detroit, Michigan can easily produce desulf slag or kish slag in quantities approximating 7,000 tons per month. The relatively small amount of such material which is capable for use as a low iron addition to sinter plants still leaves significant quantities of such waste material which eventually must be disposed of on a periodic basis.
Because of the large quantities of waste material produced by the iron and steel industries, attempts have been made to re-use iron containing waste products, which are generally considered to be uneconomical, by further treating or processing for the purpose of commercialization. Related art attempts have been made to develop methods which minimize the reprocessing procedures of waste material and which use "as-is" materials obtained directly from the mill. The returning of such products to the internal yield of the steel or iron producing mill, however, have generally been considered to be unsuccessful. These attempts include taking such "as-is" iron oxides and briquetting such materials in combination with other more iron rich products for use as commercial additions having sufficient iron content. Furthermore, the particle size is no longer an issue after briquetting has been accomplished. Usually low iron oxide containing materials as an addition to existing or conventional industrial processes has also been attempted by way of utilizing an injection process.
In light of the generally unsuccessful attempts to reuse waste material and the well recognized continuous accumulation at virtually every steel mill utilizing conventional processes, huge quantities of slag and gangue waste material continue to accumulate. Debate in the treatment of such waste material and proposed methods of disposition thereof continue without any satisfactory solution. The waste material, of the type set forth above and common to most steel mills contain an iron content of from about 30% to almost 50%. In spite of this significant iron content, the accumulated waste material, in its present form continues to be sufficiently contaminated with slag, kish, sulphur, etc. and based on the aforementioned size of the resulting fines or particles, the ability to recharge blast furnaces, as an example, is not commercially feasible. Therefore, such waste material is well recognized as having little commercial value or even a negative value when considering the cost of disposable.
Based on the above, there is a recognized need in the steel industry for a process which is both practical and economically feasible and directed to the beneficiation of desulf or kish slag waste material. Such waste material should have an iron content such that the primary product or material derived from a preferred beneficiation process would have sufficient iron content preferably in the range of substantially 90%. In addition sufficient yield from the processing of the waste material of substantially a 30% to 40% average would make commercialization of a preferred beneficiation process as well as the resulting material, feasible. For example, existing systems and methods of beneficiation generally have very limited benefits, and are only available for use with waste material containing relatively high quantities (50% or more) of iron content, all waste containing less than 50% iron necessarily being discarded before processing even commences. Moreover, in addition to discarding the low iron content waste materials before processing, such existing beneficiation methods actually produce waste material with quantities of iron in what the present invention makes a useable range. Moreover, the waste material produced by other products is not only of such an iron content as to waste a good deal of iron product, but is also of too high of an iron content for the final waste material to be potentially useable in other by-products. Specifically, such existing methods utilize common magnetic separation techniques, achieving only a preliminary separation of low iron content waste from high iron content material which is sufficient to allow the magnetic separation to effectively act upon the useable product. As a result, it would be beneficial to provide a beneficiation system and method which truly maximizes the amount of iron contained in waste material that is actually made available for use, while also maintaining the final waste product at a relatively low iron content so as to potentially increase its useability. Furthermore, such a beneficiation system should not merely "loosen" high iron content product from low iron content waste, but should be structured to more completely and effectively eliminate and/or separate the iron itself from other waste, thereby effectively utilizing a majority of the iron within the waste material rather than the higher concentrations that are easier to separate.